1 /* 2 * linux/drivers/video/backlight/pwm_bl.c 3 * 4 * simple PWM based backlight control, board code has to setup 5 * 1) pin configuration so PWM waveforms can output 6 * 2) platform_data being correctly configured 7 * 8 * This program is free software; you can redistribute it and/or modify 9 * it under the terms of the GNU General Public License version 2 as 10 * published by the Free Software Foundation. 11 */ 12 13 #include <linux/gpio/consumer.h> 14 #include <linux/gpio.h> 15 #include <linux/module.h> 16 #include <linux/kernel.h> 17 #include <linux/init.h> 18 #include <linux/platform_device.h> 19 #include <linux/fb.h> 20 #include <linux/backlight.h> 21 #include <linux/err.h> 22 #include <linux/pwm.h> 23 #include <linux/pwm_backlight.h> 24 #include <linux/regulator/consumer.h> 25 #include <linux/slab.h> 26 27 struct pwm_bl_data { 28 struct pwm_device *pwm; 29 struct device *dev; 30 unsigned int period; 31 unsigned int lth_brightness; 32 unsigned int *levels; 33 bool enabled; 34 struct regulator *power_supply; 35 struct gpio_desc *enable_gpio; 36 unsigned int scale; 37 bool legacy; 38 int (*notify)(struct device *, 39 int brightness); 40 void (*notify_after)(struct device *, 41 int brightness); 42 int (*check_fb)(struct device *, struct fb_info *); 43 void (*exit)(struct device *); 44 }; 45 46 static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness) 47 { 48 int err; 49 50 if (pb->enabled) 51 return; 52 53 err = regulator_enable(pb->power_supply); 54 if (err < 0) 55 dev_err(pb->dev, "failed to enable power supply\n"); 56 57 if (pb->enable_gpio) 58 gpiod_set_value(pb->enable_gpio, 1); 59 60 pwm_enable(pb->pwm); 61 pb->enabled = true; 62 } 63 64 static void pwm_backlight_power_off(struct pwm_bl_data *pb) 65 { 66 if (!pb->enabled) 67 return; 68 69 pwm_config(pb->pwm, 0, pb->period); 70 pwm_disable(pb->pwm); 71 72 if (pb->enable_gpio) 73 gpiod_set_value(pb->enable_gpio, 0); 74 75 regulator_disable(pb->power_supply); 76 pb->enabled = false; 77 } 78 79 static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness) 80 { 81 unsigned int lth = pb->lth_brightness; 82 int duty_cycle; 83 84 if (pb->levels) 85 duty_cycle = pb->levels[brightness]; 86 else 87 duty_cycle = brightness; 88 89 return (duty_cycle * (pb->period - lth) / pb->scale) + lth; 90 } 91 92 static int pwm_backlight_update_status(struct backlight_device *bl) 93 { 94 struct pwm_bl_data *pb = bl_get_data(bl); 95 int brightness = bl->props.brightness; 96 int duty_cycle; 97 98 if (bl->props.power != FB_BLANK_UNBLANK || 99 bl->props.fb_blank != FB_BLANK_UNBLANK || 100 bl->props.state & BL_CORE_FBBLANK) 101 brightness = 0; 102 103 if (pb->notify) 104 brightness = pb->notify(pb->dev, brightness); 105 106 if (brightness > 0) { 107 duty_cycle = compute_duty_cycle(pb, brightness); 108 pwm_config(pb->pwm, duty_cycle, pb->period); 109 pwm_backlight_power_on(pb, brightness); 110 } else 111 pwm_backlight_power_off(pb); 112 113 if (pb->notify_after) 114 pb->notify_after(pb->dev, brightness); 115 116 return 0; 117 } 118 119 static int pwm_backlight_check_fb(struct backlight_device *bl, 120 struct fb_info *info) 121 { 122 struct pwm_bl_data *pb = bl_get_data(bl); 123 124 return !pb->check_fb || pb->check_fb(pb->dev, info); 125 } 126 127 static const struct backlight_ops pwm_backlight_ops = { 128 .update_status = pwm_backlight_update_status, 129 .check_fb = pwm_backlight_check_fb, 130 }; 131 132 #ifdef CONFIG_OF 133 static int pwm_backlight_parse_dt(struct device *dev, 134 struct platform_pwm_backlight_data *data) 135 { 136 struct device_node *node = dev->of_node; 137 struct property *prop; 138 int length; 139 u32 value; 140 int ret; 141 142 if (!node) 143 return -ENODEV; 144 145 memset(data, 0, sizeof(*data)); 146 147 /* determine the number of brightness levels */ 148 prop = of_find_property(node, "brightness-levels", &length); 149 if (!prop) 150 return -EINVAL; 151 152 data->max_brightness = length / sizeof(u32); 153 154 /* read brightness levels from DT property */ 155 if (data->max_brightness > 0) { 156 size_t size = sizeof(*data->levels) * data->max_brightness; 157 158 data->levels = devm_kzalloc(dev, size, GFP_KERNEL); 159 if (!data->levels) 160 return -ENOMEM; 161 162 ret = of_property_read_u32_array(node, "brightness-levels", 163 data->levels, 164 data->max_brightness); 165 if (ret < 0) 166 return ret; 167 168 ret = of_property_read_u32(node, "default-brightness-level", 169 &value); 170 if (ret < 0) 171 return ret; 172 173 data->dft_brightness = value; 174 data->max_brightness--; 175 } 176 177 data->enable_gpio = -EINVAL; 178 return 0; 179 } 180 181 static struct of_device_id pwm_backlight_of_match[] = { 182 { .compatible = "pwm-backlight" }, 183 { } 184 }; 185 186 MODULE_DEVICE_TABLE(of, pwm_backlight_of_match); 187 #else 188 static int pwm_backlight_parse_dt(struct device *dev, 189 struct platform_pwm_backlight_data *data) 190 { 191 return -ENODEV; 192 } 193 #endif 194 195 static int pwm_backlight_probe(struct platform_device *pdev) 196 { 197 struct platform_pwm_backlight_data *data = dev_get_platdata(&pdev->dev); 198 struct platform_pwm_backlight_data defdata; 199 struct backlight_properties props; 200 struct backlight_device *bl; 201 struct pwm_bl_data *pb; 202 int ret; 203 204 if (!data) { 205 ret = pwm_backlight_parse_dt(&pdev->dev, &defdata); 206 if (ret < 0) { 207 dev_err(&pdev->dev, "failed to find platform data\n"); 208 return ret; 209 } 210 211 data = &defdata; 212 } 213 214 if (data->init) { 215 ret = data->init(&pdev->dev); 216 if (ret < 0) 217 return ret; 218 } 219 220 pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL); 221 if (!pb) { 222 ret = -ENOMEM; 223 goto err_alloc; 224 } 225 226 if (data->levels) { 227 unsigned int i; 228 229 for (i = 0; i <= data->max_brightness; i++) 230 if (data->levels[i] > pb->scale) 231 pb->scale = data->levels[i]; 232 233 pb->levels = data->levels; 234 } else 235 pb->scale = data->max_brightness; 236 237 pb->notify = data->notify; 238 pb->notify_after = data->notify_after; 239 pb->check_fb = data->check_fb; 240 pb->exit = data->exit; 241 pb->dev = &pdev->dev; 242 pb->enabled = false; 243 244 pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable", 245 GPIOD_OUT_HIGH); 246 if (IS_ERR(pb->enable_gpio)) { 247 ret = PTR_ERR(pb->enable_gpio); 248 goto err_alloc; 249 } 250 251 /* 252 * Compatibility fallback for drivers still using the integer GPIO 253 * platform data. Must go away soon. 254 */ 255 if (!pb->enable_gpio && gpio_is_valid(data->enable_gpio)) { 256 ret = devm_gpio_request_one(&pdev->dev, data->enable_gpio, 257 GPIOF_OUT_INIT_HIGH, "enable"); 258 if (ret < 0) { 259 dev_err(&pdev->dev, "failed to request GPIO#%d: %d\n", 260 data->enable_gpio, ret); 261 goto err_alloc; 262 } 263 264 pb->enable_gpio = gpio_to_desc(data->enable_gpio); 265 } 266 267 pb->power_supply = devm_regulator_get(&pdev->dev, "power"); 268 if (IS_ERR(pb->power_supply)) { 269 ret = PTR_ERR(pb->power_supply); 270 goto err_alloc; 271 } 272 273 pb->pwm = devm_pwm_get(&pdev->dev, NULL); 274 if (IS_ERR(pb->pwm)) { 275 ret = PTR_ERR(pb->pwm); 276 if (ret == -EPROBE_DEFER) 277 goto err_alloc; 278 279 dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n"); 280 pb->legacy = true; 281 pb->pwm = pwm_request(data->pwm_id, "pwm-backlight"); 282 if (IS_ERR(pb->pwm)) { 283 dev_err(&pdev->dev, "unable to request legacy PWM\n"); 284 ret = PTR_ERR(pb->pwm); 285 goto err_alloc; 286 } 287 } 288 289 dev_dbg(&pdev->dev, "got pwm for backlight\n"); 290 291 /* 292 * The DT case will set the pwm_period_ns field to 0 and store the 293 * period, parsed from the DT, in the PWM device. For the non-DT case, 294 * set the period from platform data if it has not already been set 295 * via the PWM lookup table. 296 */ 297 pb->period = pwm_get_period(pb->pwm); 298 if (!pb->period && (data->pwm_period_ns > 0)) { 299 pb->period = data->pwm_period_ns; 300 pwm_set_period(pb->pwm, data->pwm_period_ns); 301 } 302 303 pb->lth_brightness = data->lth_brightness * (pb->period / pb->scale); 304 305 memset(&props, 0, sizeof(struct backlight_properties)); 306 props.type = BACKLIGHT_RAW; 307 props.max_brightness = data->max_brightness; 308 bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb, 309 &pwm_backlight_ops, &props); 310 if (IS_ERR(bl)) { 311 dev_err(&pdev->dev, "failed to register backlight\n"); 312 ret = PTR_ERR(bl); 313 goto err_alloc; 314 } 315 316 if (data->dft_brightness > data->max_brightness) { 317 dev_warn(&pdev->dev, 318 "invalid default brightness level: %u, using %u\n", 319 data->dft_brightness, data->max_brightness); 320 data->dft_brightness = data->max_brightness; 321 } 322 323 bl->props.brightness = data->dft_brightness; 324 backlight_update_status(bl); 325 326 platform_set_drvdata(pdev, bl); 327 return 0; 328 329 err_alloc: 330 if (data->exit) 331 data->exit(&pdev->dev); 332 return ret; 333 } 334 335 static int pwm_backlight_remove(struct platform_device *pdev) 336 { 337 struct backlight_device *bl = platform_get_drvdata(pdev); 338 struct pwm_bl_data *pb = bl_get_data(bl); 339 340 backlight_device_unregister(bl); 341 pwm_backlight_power_off(pb); 342 343 if (pb->exit) 344 pb->exit(&pdev->dev); 345 if (pb->legacy) 346 pwm_free(pb->pwm); 347 348 return 0; 349 } 350 351 static void pwm_backlight_shutdown(struct platform_device *pdev) 352 { 353 struct backlight_device *bl = platform_get_drvdata(pdev); 354 struct pwm_bl_data *pb = bl_get_data(bl); 355 356 pwm_backlight_power_off(pb); 357 } 358 359 #ifdef CONFIG_PM_SLEEP 360 static int pwm_backlight_suspend(struct device *dev) 361 { 362 struct backlight_device *bl = dev_get_drvdata(dev); 363 struct pwm_bl_data *pb = bl_get_data(bl); 364 365 if (pb->notify) 366 pb->notify(pb->dev, 0); 367 368 pwm_backlight_power_off(pb); 369 370 if (pb->notify_after) 371 pb->notify_after(pb->dev, 0); 372 373 return 0; 374 } 375 376 static int pwm_backlight_resume(struct device *dev) 377 { 378 struct backlight_device *bl = dev_get_drvdata(dev); 379 380 backlight_update_status(bl); 381 382 return 0; 383 } 384 #endif 385 386 static const struct dev_pm_ops pwm_backlight_pm_ops = { 387 #ifdef CONFIG_PM_SLEEP 388 .suspend = pwm_backlight_suspend, 389 .resume = pwm_backlight_resume, 390 .poweroff = pwm_backlight_suspend, 391 .restore = pwm_backlight_resume, 392 #endif 393 }; 394 395 static struct platform_driver pwm_backlight_driver = { 396 .driver = { 397 .name = "pwm-backlight", 398 .pm = &pwm_backlight_pm_ops, 399 .of_match_table = of_match_ptr(pwm_backlight_of_match), 400 }, 401 .probe = pwm_backlight_probe, 402 .remove = pwm_backlight_remove, 403 .shutdown = pwm_backlight_shutdown, 404 }; 405 406 module_platform_driver(pwm_backlight_driver); 407 408 MODULE_DESCRIPTION("PWM based Backlight Driver"); 409 MODULE_LICENSE("GPL"); 410 MODULE_ALIAS("platform:pwm-backlight"); 411